Computer-automated surgical procedures, variously known as image-guided or navigation-based techniques, are becoming increasing popular as a way of improving the accuracy and throughput of orthopaedic, neuro-surgical and other surgical cases. Companies now engaged in this market segment include Stryker, Medtronic Surgical Navigation Technologies (a unit of Medtronic), BrainLAB, Inc., Radionics, Inc. (a subsidiary of Tyco International), Surgical Navigation Network, Inc. (a division of Cedara Software), and Visualization Technology, Inc. Theses systems assist the surgeon in the placement of instruments, location and depth of bone cuts and placement of implant components during surgery.
By way of example, the Stryker Knee Navigation System includes a “smart camera” that provides two-way communication between the instruments, a video monitor, and minimally invasive wireless “pointers” and “trackers” incorporating infrared emitters. A knee-replacement procedure begins with the surgeon inserting two tracking pins, one into the distal femur and one into the proximal tibia. Then a tracking device, positioned to face the camera, is mounted on each of the pins. Using a pointer, the surgeon touches various locations of known anatomy to establish a reference system. The system collects this information, maps it and graphically shows it on the screen.
As the surgeon physically manipulates the joint, positional information appears on the computer monitor as two-dimensional graphics in real time. Coupled with images of key anatomical points and areas of bone deficiency and soft tissue, the surgeon is able to make very precise bone resections and then place the prosthesis with great accuracy. As the surgeon prepares to remove bone for placement of the knee implant, the Knee Navigation System also provides data regarding placement of the cutting jig, enabling the surgeon to make real time angular adjustments before the first cut. The system also provides postoperative data once the implant is in place.
One of the drawbacks of these and other systems involves the way in which resections are checked for accuracy. Currently, the surgeon uses a position-calibrated “paddle” having a flat surface that is placed against a particular cut. The visualization system then registers the position of the planar system and computes an estimate of accuracy. If the surgeon is “off,” even by a few millimeters, the resection process must be re-entered and tested again. Apparatus and methods of streamlining this process would be welcomed.